The purpose of this work is to determine the enzymatic defect responsible for the various forms of glycogen storage diseases, mucopolysaccharidoses, lipidoses and other congenital diseases related to carbohydrate or lipid metabolism. Research will be continued in two directions: 1. Biopsies from patients will be analysed on the point of view of enzymic activities and some of them will also be examined with the electron microscope. 2) Several aspects of carbohydrate metabolism will be further investigated: a) The regulation of liver glycogen metabolism by glucose, insulin, glucocorticoids and cyclic AMP; b) The properties of all enzymes involved in the metabolism of glycogen in cultured human fibroblasts and the regulatory metabolism to which they are submitted. This study will concern normal fibroblasts and fibroblasts obtained from patients with type II, type III, type V, type VI and type VIa glycogenosis.